The concept of this invention was made a long time after earlier billfold concepts of my own. The earlier concepts solved the problem of a billfold bill file sutiable for double fold billfolds. The solution had been to secure the panels of the file together at the center of the lower side thereof by heat bonding or else by securing the panels together by means of the edge stitching of a billfold by having the edge stitching go through a downwardly extending boss protruding from the underside of each of the panels, the boss being disposed at the center between the ends of the billfold. This solved the problem in double fold billfolds of making it possible to fold the billfold at a time when the file was full of bills and at a time, therefore, when the radius of bending at each of the two of the two-fold bill file would be great. The problem caused by the bending of a file at a time when it is full of bills is that there is much required movement of each outer one of the panels at the bend and all along each outer panel as compared with the inner-most panel which bends the least because its radius of bending is the least.
This gradually increased the amount of required movement as one progressively considers each panel disposed outwardly from the inner-most panel of a group of bent panels is the most serious problem indeed. The problem is particularly acute because the panels must then twist and wrinkle and make the billfold buckle because the panels need to move and yet they are secured together.
I had considered the use of a file as described with the panels secured together at the center of their underside for use in a single fold billfold as well as a double fold billfold. I was troubled, however, with the fact that there is much wrinkling because the securing in that case is, therefore, at the bend in the billfold if that same structure is used in a single fold billfold which, therefore, folds at the center between its ends.
I had conceived of expensive solutions to the problem of a file of this general type for a single fold billfold and had long been involved in that creative work when it finally occurred to me that the solution for a single fold billfold is to place the position of securing the panels together substantially spaced to one side of the center between the ends of the panels where the attachment would not be in the bend area. I tried this and discovered that is worked. It worked with the multiple panel unit loosely disposed in a single fold billfold. It also worked, as I discovered, with the panel unit stitched into a single fold billfold by providing a boss protruding from all or one of the panels and extending out toward the edge of the billfold so as to be stitched into the billfold where the usual stitching goes for securing the forward and rearward walls of the billfold together, provided, however, that the stitching in the bosses was substantially spaced from the center between the right and left ends of the panels so as to dispose it outwardly beyond the portions of the panels which would be disposed between bent portions of the forward and rearward walls of the billfold at times when the billfold is in a folded condition. This has seemed to make the ideal solution for a single fold billfold currency bill file.